There’s a catch, though. Here’s what you need to know

There’s no need to speed up every time you drive by a fast-food joint with a rumbly stomach. We all succumb to the siren song of fries every once in a while, and according to a recent survey on Prevention.com, 80% of you eat fast food at least occasionally. The drive-thru mantra to remember? In moderation, friend. In moderation.

But moderation wasn’t on the minds of these brave souls. In fierce exhibitions of brand loyalty, some people will go to extremes in their efforts to lose weight. We can appreciate the urge to simplify your diet—it sure makes deciding what to have for dinner a breeze—but go too simple and you might not be getting the nutrients you need. Take the five devoted diners in our 5 Fast-Food Diets for Big Weight Loss. Sure, their meal plans might have helped them shed pounds in the short term, but we hate to think about what havoc those McNuggets can wreak over time.

Think you’re a Starbucks regular? Meet Christine Hall, a 66-year-old law librarian who ate all of her meals from Starbucks for two years. Every. Single. One.

That doesn’t mean she drank three Frappuccinos a day, of course. Hall noshed on the bistro boxes for lunch and paninis for dinner, reported Shine. Hall’s diet allowed her to drop nearly 80 pounds and qualify to be an organ donor, which are both great things.

If you’re a sucker for Snickers, do yourself a favor and stop reading now. This diet is a meal plan you do not need to know exists.

We’re talking about the convenience-store diet, a two-month experiment performed in 2010 by Mark Haub, PhD, professor of human nutrition at Kansas State University. A nutrition professor seems like an unlikely candidate for eating straight-up junk for 60 days, but his mission was to demonstrate that no matter how you get your calories, as long as you cut them back, you can drop pounds.

He did so by mostly consuming Twinkies, Doritos, and snack cakes. But he also supplemented with vitamins, exercise, protein shakes, and some fresh veggies. Here’s the scary part: Professor Haub lost 27 pounds and his good HDL cholesterol went up. But you might want wait for a more long-term guinea pig before you toss the kale for Kit Kats.

Burritos can be a diet food if you order them right. Just ask a guy named Eric over at Chipotless.com: He ate at the Tex-Mex chain twice a day for about nine months. (After that, he stopped posting, which is sort of unsettling.)

Eric’s secret order? A burrito bowl for breakfast and an identical one for lunch. He wrote that he consumed about 1,480 calories per day and lost 91 pounds, supplementing the burritos with a single egg in the morning. While we can’t imagine eating a single fast food for nearly a year, you could do worse. Eric’s burrito bowl was stuffed with peppers, onions, steak, two kinds of salsa, cheese, sour cream, guacamole, and romaine lettuce. Not bad for fast food.

Anyone who’s seen Super Size Me, Morgan Spurlock’s documentary about eating only McDonald’s for a month, is familiar with this diet (and hopefully hasn’t tried to replicate it). Spurlock ate breakfast, lunch, and dinner at the Golden Arches and gained about 25 pounds, along with lots of negative side effects.

Of course, he didn’t solely rely on McDonald’s lower-cal options (most of which we’ve stripped of their health halos here.) But one man, nicknamed the “McRunner,” ran the Los Angeles Marathon powered only by McDonald’s calories for a month prior. He ran his best time ever, at 2:36:14.

“I feel as good as I've ever felt,” he told Runner’s World. “I actually ended up losing a bit of body fat during all of this.”

Good for him! But we definitely don’t dare you to try this one—even if you’re training for a marathon.

You’ve heard of Jared’s extreme Subway diet. Fewer of us remember Christine Dougherty, the taco belle, who lost 54 pounds in two years by dining at the chain a few times a week.

In 2009, Taco Bell coined her unique way of eating the “Drive-Thru Diet.” That’s a little misleading: According to a news release on Taco Bell’s website, Dougherty lost the weight by swapping her greasy fast-food habit for items from Taco Bell’s lower-fat “Fresco” menu. The rest of the time, she made “other sensible choices” and cut her calories to just 1,250 per day—which is enough to make almost anyone lose weight. So we applaud her, but it’d take a lot of cute Chihuahuas to get us onboard with this one.